Control apparatus



p 1954 B. H. PINCKAERS CONTROL APPARATUS 2 Sheets-Sheet 1 Filed July 51, 1961 Nm w. mw

INVENTOR.

BALTHASAR H. PINCKAERS ATTORNEY I p 1, 1964 B. H. PINCKAERS CONTROL APPARATUS 2 Sheets-Sheet 2 Filed July 31, 1961 h M N INV EN TOR. BALTHASAR H. PINCKAERS BY A TTOENE') United States Patent 3,147,000 CONTROL APPARATUS Balthasar H. Pinckaers, Edina, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn a corporation of Delaware Filed July 31, 1961, Ser. No. 127,970 8 Claims. (Cl. 268-33) My invention relates generally to improved control apparatus and more specifically to a new and improved semiconductor electronic circuit which may be used for controlling automatic door opening and closing systems.

It is an object of my invention to provide a new and different approach to the control of automatic door operating systems such as may be found in the pedestrian doors of many supermarkets and the like. Prior art generally shows the use of electrical controls wherein the switching operations and control current are directly the function of electro-mechanical relays. These prior art systems have the disadvantage of requiring either a high amount of voltage or a high current flow through the switches that necessarily must be placed on approach mats and safety mats which are placed on either side of a door to be controlled. My invention provides a system whereby a very small amount of current and a very small voltage is required for control purposes. Thus, I provide a system offering a greater safety factor than does the prior art.

Another object of my invention is to provide a more reliable control apparatus. My experience in the control field has indicated that prior art systems using a complex configuration of relays have a low reliability factor. This may be attributed to the fact that they require much mechanical switching, many contacts and a relatively high operating current or voltage. My invention requires the use of a single relay and a low operating voltage. Thus, I have increased the reliability of control systems of this type.

Another object of my invention is to provide a control system which may be readily serviced or repaired by on the spot trouble shooting. In one embodiment of my invention, I have provided three distinctive lights placed strategically at different electrical intervals in the circuit configuration. These lights then, in a manner to be discussed later, will provide an immediate indication of the area wherein trouble has arisen. By a quick glance at the sequence of light operation, a technician, or even a non-technician, can readily isolate any trouble which might arise to a specific area and to a very few possibly malfunctioning parts.

FIGURE 1 is a schematic representation of a preferred embodiment of my invention, showing the circuits wherein I place lights or current indicating means to facilitate fast trouble shooting.

FIGURE 2 is a schematic representation of another embodiment of my invention wherein I show my control circuit attached to a typical door operating motor system.

FIGURE 3 shows a typical doorway together with a normal placement of approach and safety mats which are contemplated to be used in conjunction with my control apparatus when used in automatic door operating systems.

Referring now to the drawings, FIGURE 1 shows a transformer having a primary Winding 11 which is connected to a suitable source of alternating current which may be closed and interrupted by a power switch 12. Secondary winding 13 of transformer 10 is shown with a tap 14 which is connected through a capacitor 15 to a collector electrode 16 of a transistor or current con trol device 17, also having emitter and base electrodes 47 and 19. The transistor or semiconductor device 17 has 3,147,000 Patented Sept. 1,, 1964 a pair of input electrodes and a pair of output electrodes. A base 19 and an emitter 19 comprise the input electrodes and the base 19 and the collector 16 comprise the output electrodes. One terminal of secondary 13 is connected through a rectifier 18 to the base 19 of the transistor or current control device 17. The other terminal of secondary 13 is connected through a rectifier 20 to a stationary contact 25a of a SPDT switch 25 operated by a relay 85. Switch 25 also includes a movable contact 26 and another stationary contact 29. Relay contact 26 is connected via a lead 27 and a junction point 28 on a conductor 28a to the base 19. Contact 29 is connected to a junction point 30.

The lower lead of a secondary winding of transformer 10 is connected through a conductor 35a and an incandescent lamp 36 to the junction point 30. The upper lead of secondary 35 is connected through a conductor 35b and a switch 37 to the junction point 30. Disposed across winding 35 is an incandescent lamp 38 shown connected to conductors 35a and 3512 at points 39 and 40. The upper lead of secondary 35 is also connected through point 40 to an approach mat switch which is in turn connected through a junction 49 and a current limiting resistor 46 to the emitter electrode 47 of transistor 17. An incandescent lamp 48 is shown disposed between the junction 49 and a junction 50 on lead 35a.

A resistor 51 is shown disposed between a pair of junction points 52 and 53 on conductors 28a and 35a, and a resistor 54 is shown disposed between the junction points 30 and 28.

The lower lead of a secondary winding of the transformer 10 is shown connected through a rectifier 61 to a conductor 62 and from a junction 62a thereon to an emitter electrode 63 of a transistor 64. Base 65 of transistor 64 is shown connected by a conductor 6611 having junctions 68 and 75 thereon and through a resistor 66, a conductor 66]; and junction point 41 to collector 16 of transistor 17. A capacitor 67 is shown disposed between the junction point 68 and a junction 69 on conductor 62, and a resistor 70 is shown disposed between the junction point and a junction 76 on conductor 62.

The emitter 77 of a transistor 78 is shown connected through a resistor 79 and junction point 62a to the emitter 63 of transistor 64-. The base 80 of transistor 73 is connected to lead 81 which in turn connects the collector 71 of transistor 64 to resistor 84. The upper terminal ondary 13 through rectifier 61 to the lower terminal of secondary 60 of transformer 10. Emitter 77 of transistor 78 is connected through junction point 92, resistor 93, and lead 94 to the upper terminal of secondary 60 via junction point 73 and the lead 60a. Lead 60a is connected through resistor 74 to the lead 87. A resistor 93 is connected between the collector 83 of transistor 78 and the base 65 of transistor 64. Disposed between the junction point 73 and collector 71 is a resistor 84, the junction point 73 being the point whereat the leads 60a and 94 are connected to each other. A rectifier 95 is connected in parallel with coil 82 of relay 85. Power control contacts and leads of the relay 35 are shown generally at numeral 96.

As a broad generalization, the transistor 17 with its directly related components comprises the basic control circuit. The transistors 64 and 78 with their associated components comprise a direct current amplifier with positive feedback for switching action for amplifying the signal generated in the basic control circuit.

An embodiment of my invention shown in FIGURE 2 discloses a transformer 110 having a primary winding 111 which is adapted to be energized by a suitable source of alternating current. Across primary 111 is an incandescent lamp 112 shown attached at points 113 and 114. The upper lead of secondary winding 115 of transformer 11% is connected through a rectifier 116 and a lead 122 to collector 117 of a transistor 118. The lower lead of secondary 115 is attached through a lead 148 and relay coil 119 to the emitter 120 of the transistor 118. A filter capacitor 125 is disposed between points 126 on lead 122 and 127 on lead 148. Contact 132 of approach mat switch 133 is connected to a point 129 on a lead 123. Contact 134 of the approach mat switch 133 is connected through a junction point 135 to a contact 136 on a safety mat switch 137 and through the junction point 135 and through a lead 124 to base electrode 121 of the transistor 118. A resistor 130 is connected between leads 122 and 123 at points 129 and 131. Contact 138 of the safety mat switch 137 is connected to movable contact 139 of SPDT switch 119a of relay 119 which switch also includes stationary contacts 140 and 146. Stationary contact 146 is connected to the junction point 129. Stationary contact 140 of the relay 119 is connected to a junction point 145 on the lead 148. A capacitor 147 is disposed between base 121 of the transistor 118 and the lead 148 which is connected to the lower terminal of the secondary 115.

Leads 152 and 153 are connected across the source at points 154 and 155 respectively. Line 152 passes through the load contacts of relay 119 which are shown generally at 156 and on to a point 157 which is at the upper terminal of a door-hold solenoid coil 158. The door-hold coil 158 is shown disposed between lines 152 and 153. A motor start relay 160 is connected to line 153 at point 159. Lead 162 of coil 161 of the motor start relay 160 is shown connected to the lower lead of a motor run winding 163. Contact 164 of motor start relay is shown connected through capacitor 165 to motor start winding 166. The upper leads of motor run winding 163 and motor start winding 166 are connected through limit switch 167 to the junction point 157. Relay contact 168 is connected to the junction point 159 on lead 153.

FIGURE 3 shows a typical placement of approach mat and safety mat with respect to a door to be controlled showing the approach mat and the safety mat respectively as the members (switches) 133 and 137.

Operation A typical use of my control apparatus is contemplated to be the control of automatic door openers. Therefore, for the purpose of discussing the operational sequence of my invention, it will be assumed to be operating in the function of a door control apparatus.

' FIGURE 1 shows a preferred embodiment of the control circuit which includes an amplifier and a load relay together with its associated contacts. Assuming a 120 volt power source is applied to primary 11 of transformer 10, voltages in the order of 15 volts should appear across each section of the secondary winding 13. The center tap of winding 13 is connected through a capacitor 15 to the collector element of transistor 17. It will be obvious to those skilled in the art that center tapped secondary 13 may also be two separate secondary windings. The upper lead of secondary 13 is connected through a rectifier 13 to the base electrode of transistor 17. The lower lead of secondary 13 is connected through a rectifier 20 and through relay contacts 25.. and 26 to the base elec- 4 formed across the same elements of transistor 17 and capacitor 15 at such time as relay contacts a and 26 are closed.

Across secondary winding 35 should appear a voltage in the order of 6.3 volts. The voltage across secondary 35 and its associated current paths will act to control the conductance of transistor 17 in the following manner: Considering a half-cycle of alternating current supplied from the 6.3 volt secondary winding of transformer 19; when the upper terminal of the winding is instantaneously positive, a current path can be traced from the upper terminal of secondary winding 35 through the approach mat switch 45 (if closed), through the resistor 46, through the common base connected transistor 17 from emitter 47 to base 19, through normally closed contacts 29 and 26 of relay 85 through lamp or current indicating means 36 and back to the lower terminal of secondary 35.

Transistor 17 is thus rendered conductive during the half-cycle when the upper terminal of secondary winding is positive. also its upper terminal is positive, with respect to tap 14, during the same half-cycle. Therefore, a further current path can be then traced from the upper terminal of windwhich the above noted polarities prevail, the current in resistor 66 reaches the required trigger value, the coil 82 of relay 85 will suddenly he completely energized. The

relay then will close power contacts 96 to energize the door motor load or circuit to be controlled.

Relay 85 now having been energized acts to close contacts 25a and 26 and to remove the short across resistor 54 which was created as a result of contacts 26 and 29 of relay 85 being closed.

Considering switches 45 and 37 as approach and safety mat switches respectively; as a person steps from the approach mat to the safety mat, switch 45 opens and switch 37 closes. However there may be a time delay, for example in the case of a slow moving older person, between the opening of switch 45 and the closing of switch 37. Therefore, for safety reasons, it is necessary to prevent the door from immediately closing, so that the person slowly crossing the threshold is not struck by the closing door. For this reason, a relay drop-out delay is provided by capacitor 15 which discharges through resistors 66 and 70. As long as the discharge current is above the value at which the switching circuit suddenly de-energizes the relay coil, the door will remain open.

- As switch 45 opens, the first current control circuit or the control circuit which may be considered sensitive to a first predetermined condition, such as the condition created by someone stepping on the approach mat, is no longer closed. Sequential to the opening of the first control circuit, safety mat switch 37 is closed as a result of a person stepping on the safety mat in the course of his normal progression through the doorway which may be considered a second predetermined condition which acts to form or close a second current control circuit. Thus then the circumstances are: relay is energized, switch 45 is open and switch 37 is closed. This results in a second current control circuit wherein a different mode of operation occurs. Under these conditions, considering now the second one-half cycle of alternating current; when the lower terminal of secondary 35 is positive and considering that relay 85 is in its energized position as a result of current flow created by the sequence of operation initiated by the closing of the approach mat switch, a current path can now be traced from the lower leadof secondary 35 through lamp 48 and resistor 46 to the emit- The secondary winding 13 is so arranged that i ter electrode 47 and through the base 19 of transistor 17, through resistor 54 and safety mat switch 37 to the upper lead of secondary 35 of transformer 10. During this onehalf cycle the current path for charging the capacitor 15 can be traced from the bottom terminal of secondary 13 which is now positive, through rectifier 20, through relay contacts 25a and 26, from the base electrode to the collector of transistor 17 and through capacitor 15 back to the center tap 14 of secondary 13. Capacitor 15 will now continue to be charged through this current path.

It is important that the door should be incapable of opening as a result of someones stepping on the safety mat switch without first having depressed the approach mat switch since the door will open across the safety mat. Contacts 25a and 26 act to close the circuit from the lower portion of the secondary 13 and through transistor 17 from .base to collector only after a current has first been established through relay 85 as a result of some ones having depressed the approach mat switch.

When the door is in a closed position and relay 85 is de-energized, transistor 17 cannot be rendered conductive by the depression of approach mat 45 when someone is standing on the safety mat switch. By observing the circuit shown in FIGURE 1, it can be seen that when switches 37 and 45 are both closed, the emitter and the base of the transistor are substantially at the same potential. It is also necessary, once the door is opened by closure of the approach mat switch, that the door will remain open when subsequently the safety mat switch is closedor when both safety mat switch and approach mat switch are closed. For eXample someone may depress the approach mat switch, which opens the door provided the safety mat switch is not closed, walk through the door onto the safety mat, which closes the safety mat switch, while someone else approaching the door has again depressed the approach mat switch. It is the function of normally closed relay contact 29 in conjunction with resistors 54- and 51 to provide this function. It has been shown that starting with the relay de-energized, the relay can only be energized by closure of switch 45 (while 37 is open). It has been further shown that when the relay is energized it can be maintained in this condition by closed switch 37 (while 45 is open). It is also maintained in this latter condition when both switches 45 and 37 are closed. When both 45 and 37 are closed the conditions in the control circuit are the same as the ones which originally caused relay energization except that now the emitter-base current through transistor 17 is substantially reduced. However, this current is sufliciently high to hold relay 85 energized;

It will be noted that the control circuit contains three bulbs or incandescent lamps. These lamps, each of which has distinctive characteristics such as a color varying from that of the others, are utilized for the purpose of indicating the presence of current in particular areas of the control circuit. Lamp 38 is connected directly across secondary winding 35 of transformer 10. Lamp 38 will indicate the presence of power at all times across secondary 35. Lamp 48 is connected in parallel with the first current control circuit and will consequently light at such times as the current path is closed through the first current control circuit by the approach mat switch 45. Lamp 36 is connected in parallel with the second current control circuit and will consequently be lighted at such times as the second current control circuit is closed by safety mat switch 37. It will be noted that lamps 36 and 48 appear in the control current path alternate to the ones in which they are intended to indicate the presence of current. These lamps, by virtue of their design, provide a very low resistance when cold and will not have sufiicient voltage drop across them to cause them to light when they are connected in series with the other resistances presented in the control current paths and thus serve only inthe capacity of a low resistance conductor. As previously pointed out, it is very desirable to isolate any troubles which might arise to a specific area or group of possibilities. These lamps accomplish this purpose and greatly facilitate servicing of the control circuit. By a quick glance at the lamps during operational sequence, one will observe that voltage must be present across secondary of transformer 10 if the lamp 38 is lit. Lamp 48 is connected across the 6.3 volt winding 35 when switch is closed. If lamp 48 lights when the switch 45 is depressed and only when switch 45 is depressed, this will indicate that the approach mat switch is functioning properly. If lamp 45 remains lit at all times, this will indicate that the approach mat is shorted. If the lamp lights in proper sequence, this will indicate that a malfunction is elsewhere in the circuit. If lamp 36 lights when switch 37 is closed, and only when this switch is closed, it will be known that the safety mat switch is working properly and, as in the case of lamp 48, when the lamp 36 is operating in proper sequence it will be known that the malfunction is to be found elsewhere in the circuit.

The operation of the embodiment of my invention shown in FIGURE 2 is as follows:

When a source of alternating current is applied across primary 111, a resultant voltage is induced in secondary 115 of transformer 110. The secondary 115 together with rectifier 116 and filter capacitor 125 forms a DC. power source having the junction point 127 as its positive terminal and the junction point 126 as its negative terminal. A current path can be traced from junction point 127 through relay coil 119, from the emitter to the collector of transistor 118 and on to junction 126. Current flow through transistor 118 is controlled by a circuit between the base 121 and the emitter of the transistor which includes two mat switches, the approach mat switch and the safety mat switch. These mat switches are effectively in parallel. As a person steps on the approach mat switch 133, a current path can be traced from the base electrode, through the approach mat switch 133, through resistor to junction point 126, through the power source to junction point 127, through the relay coil 119 and back to the emitter electrode. Upon the closing of approach mat switch 133, a current will be caused to flow from emitter to collector of the transistor. This emitter to collector current will cause current to flow through relay coil 119 to in turn cause the relay arm 139 to deflect and make connection with contact 146. By this action, safety mat switch 137 is placed in parallel with approach mat switch 133. As a person progresses through the door, safety mat switch 137 will be depressed and the approach mat switch 133 will be opened. Thus, current flow from emitter to collector will be maintained by virtue of the current control circuit being maintained closed through the safety mat switch.

The capacitor 147 acts to delay the drop out of relay 119. 'As pointed out in the discussion of FIGURE 1, it is desirable to provide a small time lag wherein the relay remains energized for the purpose of allowing slow moving traffic to proceed from one mat to the other without fear of the doors beginning to close during the progression of this traffic. When both mat switches are open after capacitor 147 has been charged, the capacitor then discharges through the emitter-base input circuit of the transistor 118. Therefore a current B times as large flows in the relay coil (where B is gain of transistor) creating a voltage drop which is of such a polarity as to oppose the discharge of capacitor 147. Therefore the time constant formed by capacitance of capacitor 147 and relay coil resistance is effectively multiplied by the transistor gain. This results in relatively long drop-out delay for the relatively small capacitance of capacitor 147.

The relay contacts 139, 140, and 146 have the purpose of assuring that current flow through the transistor cannot be accomplished by depressing the safety mat switch without first having depressed the approach mat switch. This purpose then provides a safety feature of not allowing the door to be opened by a person approaching from the wrong direction. Also, if a person is standing on the safety mat, depression on the approach mat will not open the'door by reason of the fact that when safety mat 137 is depressed out of proper sequence it acts to short the base of transistor 118 to the positive terminal of the DC. supply and thus prevents conduction in the transistor to energize the relay.

It is apparent that the load contacts shown generally at numeral 156 will be closed at such time as current is flowing through the transistor. Thus, the AC. source voltage will be applied through leads 152 and 153 and through load switch 156 to solenoid 158. This source voltage will also be applied between points 159 and the upper leads of motor windings 163 and 166 at such times as overload switch 167 is not depressed. The motor windings 163 and 166, capacitor 165 and motor start relay 160 will act in the manner which is usual and well-known in the motor art. A heavy starting current through the run winding 163 and the relay coil 161 will act to cause contacts 164 and 168 to close to in turn apply the source voltage to start winding 166 for the purpose of giving an additional boost to start the motor running. At such time as the door has been completely opened, limit switch 167 will open and de-energize the motor. Solenoid 158 will act to hold the door open. While it is obvious that my invention provides a unique improvement in automatic door control operations, it will be apparent to those skilled in the art that my control apparatus may be readily adapted for any use requiring the functions which it provides. Therefore, I request that my invention be limited only by the scope of the appended claims.

I claim:

1. Semiconductor control apparatus comprising: a semiconductor device having a pair of input electrodes and a pair of output electrodes; first means sensitive to a first predetermined condition; second means sensitive to a second predetermined condition; a low voltage source; control means including switch actuating output means; means connecting said first means in a controlling relation to the input electrodes of said semiconductor device and to the low voltage source to thereby energize said control means to energize said switch actuating means; means controlled by said output means when said control means is in the energized condition to connect said second means in a controlling relation to the input electrodes and to the low voltage source to maintain said switch actuating means in an energized position.

2. Control apparatus for use in control operations wherein a first signal is required to actuate a means to be controlled and a second signal is required to maintain the means to be controlled in an actuated position, comprising: a current control device having a pair of input electrodes and a pair of output electrodes; first means sensitive to a first predetermined condition; second means sensitive to a second predetermined condition; a low voltage source; control means including circuit closing output means, said control means being connected to said output electrodes; means connecting, said first means in a controlling relation to the input electrodes of said current control device and to the low voltage source to thereby energize said control means to energize said circuit closing means; means connecting said second means to said low voltage source and in a controlling relation to said input electrodes to maintain the said circuit closing means in an energized position; and further circuit closing means adapted to be closed by said output means operable to prevent an initial energization of said output means in the presence of said second means sensitive to a second predetermined condition when said output means has not been first energized by the presence of said first means sensitive to a first predetermined condition.

3. Control apparatus as described in claim 2, wherein a first distinctive current indicating means adapted to be connected across said low voltage source in the presence of said first predetermined condition and means operable to connect said first distinctive current indicating means in thepresence of said first predetermined condition; and second distinctive current indicating means adapted to be connected across said low voltage source in the presence of said second predetermined condition and means operable to connect said second distinctive current indicating means in the presence of said second predetermined condition are utilized.

4. In a control apparatus for use in control operations where a first signal is required to actuate a means to be controlled and a second signal is required to maintain the means to be controlled in an actuated position, comprising a current control device having a pair of input electrodes and a pair of output electrodes, first means sensitive to a first predetermined condition, second means sensitive to a second predetermined condition, a low voltage source, control means including circuit closing means, output means, means connecting said first means in a controlling relation to the input electrodes of said current control device and to the low voltage source to thereby energize said control means to energize said circuit closing means, means connecting said second means to said low voltage source and in a controlling relation to said input electrodes to maintain the said circuit closing means in an energized position, and further circuit closing means adapted to be closed by said output meansoperable to prevent an initial energization of said output means in the presence of said second means sensitive to a second predetermined condition when said output means has not been first energized by the presence of said first means sensitive to a first predetermined condition: first distinctive current indicating means connected across said low voltage source in the presence of said first predetermined condition and means operable to connect said first distinctive current indicating means across said source in the presence of said first distinctive indicating means across said source in the presence of said first predetermined condition; second distinctive current indicating means adapted to be connected across said low voltage source in the presence of said second predetermined condition and means operable to connect said second distinctive current indicating means across said sourcein the presence of said second predetermined condition; and further distinctive current indicating means and means operable to connect said further distinctive current indicating means connected across said low voltage source to indicate the presence or absence of energization of said low voltage source.

5. A control circuit for use in controlling an automatic door including a relay for energizing a door operator actuator and an electronic control circuit for the relay control wherein a first signal is required to open the door and a second signal is operative to maintain the door in an open position: the improvement which comprises semiconductor current control means having a pair of input electrodes and a pair of output electrodes; an approach switch adapted to provide the first signal; a safety switch adapted to provide the second signal; a low voltage source; output means to be connected to control a door actuator; means connecting said output means to said output electrodes; means connecting the approach switch in controlling relation to the input elec-- trodes of said semiconductor current control means and to said low voltage source to thereby actuate said output means; and means controlled by said output means when in said actuated condition to connect said safety switch in controlling relation to said input electrodes and to the low voltage source to maintain the door open so long as the safety switch is in an actuated condition.

6. In a control apparatus for use in controlling an automatic door including a door operator, an electronic control circuit for the operator, a low voltage source for the electronic control circuit, and output means connected to control the door operator wherein a first signal is required to open the door and a second signal is operative to maintain the door in an open position: the improvement which comprises an electronic current control device having a pair of input electrodes and a pair of output electrodes; an approach mat switch adapted to provide said first signal; a safety mat switch adapted to provide said second signal; means connecting the approach mat switch in a controlling relation to the input electrodes of said electronic current control device and to said low voltage source to thereby actuate said output means to open the door; means connecting the safety mat switch in a controlling relation to the input elec trodes of said electronic current control device and to the low voltage source; circuit means including switch means adapted to prevent actuation of said output means by said safety mat switch when said output means has not been first actuated by said approach mat switch, said switch means being operated by said output means when in said actuated condition to connect said safety mat switch in a controlling relation to said input electrodes and to said low voltage source to maintain said output means in an energized position so long as said safety switch is maintained closed.

7. Control apparatus for use in controlling a relay wherein a first signal is required to actuate said relay and a second signal is operative to maintain the relay in an actuated position comprising: an electronic current control device having a pair of input electrodes and a pair of output electrodes; output means connected to control the relay; a first switch adapted to provide a first signal; a second switch adapted to provide a second signal; a low voltage source; a pair of voltage sources adapted for alternate use to provide output current; means connected a first of said pair or" voltage sources across the output electrodes of said current control device; means connecting said first switch in a controlling relation to the input electrodes of said current control device and to the low voltage source to thereby actuate said output means to operate the relay; means adapted to prevent actuation of said output means by said second switch when said output means has not been first actuated by said first switch, including a first circuit closing device actuated by said output means operable to connect a second of said pair of voltage sources having opposite phase relationships to thereby allow current flow through said current control device in the presence of said second signal; switch closing means controlled by said output means for closing said switch means when said output means is actuated by the presence of a first predetermined condition; means controlled by the output means when in said actuated condition to connect said second switch in a controlling relation to the input electrodes and to the low voltage source to maintain the said output means in an energized position; first distinctive current indicating means connected across said low voltage source in the presence of said first signal and means operable to connect said first distinctive indicating means across said source in the presence of said first signal; and second distinctive current indicating means adapted to be connected across said low voltage source in the presence of said second signal and means operable to connect said second distinctive current indicating means across said source in the presence of said second signal.

8. Control apparatus for use in controlling a relay wherein a first signal is required to actuate said relay and a second signal is operative to maintain said relay in an actuated position: a semiconductor current control device having a pair of input electrodes and a pair of output electrodes; a first switch adapted to provide the first signal; a second switch adapted to provide the second signal; a low voltage source; relay means; output means controlling said relay means; means connecting said output means to said output electrodes; means connecting said first switch in a controlling relation to the input electrodes of said semiconductor device and to the low voltage source to thereby actuate said output means; and circuit means including switch means controlled by said output means connected serially with said second switch and adapted to connect said second switch in a cont-rolling relation to send said input electrodes and to the low voltage source in the presence of said first signal to maintain said relay actuated so long as said second switch is in an actuated position.

References Cited in the file of this patent UNITED STATES PATENTS 2,843,376 Osuch et a1 July 15, 1958 2,891,156 Crow June 16, 1959 2,896,130 Tompkins July 21, 1959 2,906,926 Bauer Sept. 29, 1959 2,947,916 Beck Aug. 2, 1960 2,956,179 Yragui Oct. 11, 1960 3,039,038 Weible June 12, 1962 3,041,507 Rose June 26, 1962 

5. A CONTROL CIRCUIT FOR USE IN CONTROLLING AN AUTOMATIC DOOR INCLUDING A RELAY FOR ENERGIZING A DOOR OPERATOR ACTUATOR AND AN ELECTRONIC CONTROL CIRCUIT FOR THE RELAY CONTROL WHEREIN A FIRST SIGNAL IS REQUIRED TO OPEN THE DOOR AND A SECOND SIGNAL IS OPERATIVE TO MAINTAIN THE DOOR IN AN OPEN POSITION: THE IMPROVEMENT WHICH COMPRISES SEMICONDUCTOR CURRENT CONTROL MEANS HAVING A PAIR OF INPUT ELECTRODES AND A PAIR OF OUTPUT ELECTRODES; AN APPROACH SWITCH ADAPTED TO PROVIDE THE FIRST SIGNAL; A SAFETY SWITCH ADAPTED TO PROVIDE THE SECOND SIGNAL; A LOW VOLTAGE SOURCE; OUTPUT MEANS TO BE CONNECTED TO CONTROL A DOOR ACTUATOR; MEANS CONNECTING SAID OUTPUT MEANS TO SAID OUTPUT ELECTRODES; MEANS CONNECTING THE APPROACH SWITCH IN CONTROLLING RELATION TO THE INPUT ELECTRODES OF SAID SEMICONDUCTOR CURRENT CONTROL MEANS AND TO SAID LOW VOLTAGE SOURCE TO THEREBY ACTUATE SAID OUTPUT MEANS; AND MEANS CONTROLLED BY SAID OUTPUT MEANS WHEN IN SAID ACTUATED CONDITION TO CONNECT SAID SAFETY SWITCH IN CONTROLLING RELATION TO SAID INPUT ELECTRODES AND TO THE LOW VOLTAGE SOURCE TO MAINTAIN THE DOOR OPEN SO LONG AS THE SAFETY SWITCH IS IN AN ACTUATED CONDITION. 